1. Field of the Invention
The present invention relates to a passive matrix display device. In particular, the invention relates to a passive matrix display device using a light emitting element such as an organic electroluminescence element for a pixel portion.
2. Description of the Related Art
In recent years, a so-called self-light emitting type display device having a pixel including a light emitting element such as a light emitting diode (LED) has attracted attention. As a light emitting element used for such a self-light emitting type display device, there are known an organic light emitting diode (OLED), an organic EL element, and an electroluminescence (EL) element, which are used for an organic EL display and the like.
Since a light emitting element such as an OLED is a self-light emitting type, it is more advantageous than a liquid crystal display in high visibility of pixel, fast response without requiring a back light, and the like. The brightness of a light emitting element is controlled by the amount of current flowing therethrough.
A display device using such a self-luminous light emitting type element is driven by a passive matrix method or an active matrix method. According to the active matrix method, each pixel includes a control circuit having several switching thin film transistors (also referred to as TFTs) and light emission or non-light emission of each pixel is controlled by the control circuit of each pixel. On the other hand, in a passive matrix display device, plural column signal lines and plural row signal lines intersect each other and an organic EL element is disposed at each intersection thereof. Accordingly, a potential difference is generated in an area sandwiched between a selected row signal line and a column signal line that outputs a signal, thereby an organic EL element (called a pixel) emits light when a current flows.